What is Elementary particles: Definition and 102 Discussions

In particle physics, an elementary particle or fundamental particle is a subatomic particle with no (currently known) substructure, i.e. it is not composed of other particles. Particles currently thought to be elementary include the fundamental fermions (quarks, leptons, antiquarks, and antileptons), which generally are "matter particles" and "antimatter particles", as well as the fundamental bosons (gauge bosons and the Higgs boson), which generally are "force particles" that mediate interactions among fermions. A particle containing two or more elementary particles is called a composite particle.
Ordinary matter is composed of atoms, once presumed to be elementary particles—atomos meaning "unable to be cut" in Greek—although the atom's existence remained controversial until about 1905, as some leading physicists regarded molecules as mathematical illusions, and matter as ultimately composed of energy. Subatomic constituents of the atom were first identified in the early 1930s; the electron and the proton, along with the photon, the particle of electromagnetic radiation. At that time, the recent advent of quantum mechanics was radically altering the conception of particles, as a single particle could seemingly span a field as would a wave, a paradox still eluding satisfactory explanation.Via quantum theory, protons and neutrons were found to contain quarks – up quarks and down quarks – now considered elementary particles. And within a molecule, the electron's three degrees of freedom (charge, spin, orbital) can separate via the wavefunction into three quasiparticles (holon, spinon, and orbiton). Yet a free electron – one which is not orbiting an atomic nucleus and hence lacks orbital motion – appears unsplittable and remains regarded as an elementary particle.Around 1980, an elementary particle's status as indeed elementary – an ultimate constituent of substance – was mostly discarded for a more practical outlook, embodied in particle physics' Standard Model, what's known as science's most experimentally successful theory. Many elaborations upon and theories beyond the Standard Model, including the popular supersymmetry, double the number of elementary particles by hypothesizing that each known particle associates with a "shadow" partner far more massive, although all such superpartners remain undiscovered. Meanwhile, an elementary boson mediating gravitation – the graviton – remains hypothetical. Also, as hypotheses indicate, spacetime is probably quantized, so there most likely exist "atoms" of space and time themselves.

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  1. Rayan

    I Neutrino-Atom Elastic Scattering: Insights from Particle Physics

    What happens generally when a neutrino/anti-neutrino collides with a light vs heavy atom? My guess is, since neutrinos have very low cross section, their interaction is weak and therefore it will be an elastic scattering! For example: $$ \overline{\nu} + He^3 \rightarrow \overline{\nu} + He^3...
  2. V

    B How does exchange of elementary particles result in a force?

    Homework Statement:: I came across the following in an online article. I am unable to understand how these elementary particles cause a force to exist. "Each of the four forces results from the exchange of force-carrier particles.". Above statement is taken from...
  3. R

    B Electrons, quarks and gluons made from something or nothing?

    Most articles said electrons, quarks and gluons are indivisible thus have no compositions unlike the other particles. So, does that means electrons, quarks and gluons are composed of nothing and these elementary particles are indeed 100% void?
  4. R

    B Are these actually real electrons?

    I'm curious whether the scientists actually show the real electron in this video. Thoughts?
  5. J

    A Griffith's Elementary Particles Section 9.7 Electroweak Unification

    1. On pg. 343 Griffith's expresses the weak current in terms of left-handed doublets. jμ± = ##\bar χ_L##γμτ±##χ_L## ##χ_L## = ##\begin{pmatrix} ν_e \\ e \end{pmatrix}_L## ##\tau^+## = ##\begin{pmatrix} 0 & 1 \\ 0 & 0 \end{pmatrix}## , ## \tau^- ## = ##\begin{pmatrix} 0 & 0 \\ 1 & 0...
  6. J

    B String Theory & Elementary Particles: What's Real?

    If string theory is correct does it mean that elementary particles like photons, electrons, and quarks don't really exist or does it mean they do but are made of cosmic strings and so therefore are not elementary?
  7. J

    I Group Theory Appearing in Griffith's Elementary Particles (2nd Ed.)

    Hello, I'm trying to make sense of some of the group theoretic discussion found in Griffith's Introduction to Elementary Particles. I have had a fair amount of exposure to elementary group theory, but no representation theory, and have some specific questions related to this which refer to the...
  8. nmsurobert

    B Can elementary particles truly be at rest in an E field?

    I'm working on E fields and particles in E fields, and I was wondering if particles are ever truly accelerated from rest. I did some reading on how accelerators work and cathode tubes, but it seems that particles are always in some type of motion. Is this just a thing for introductory level...
  9. kmm

    Particle Is Griffiths Introduction to Elementary Particles up to date?

    I have a copy of Griffiths Introduction to Elementary Particles (1st Edition) and was thinking of beginning to work through it. I was curious if anyone knows if this text is sufficiently up to date or if there have been any major developments in particle physics that would make it worth getting...
  10. jgarrel

    Quantum Field Theory-Mass spectrum of Lagrangian

    Homework Statement We are given the Lagrangian density: $$ \mathcal{L}=\partial^\mu \phi ^* \partial_\mu \phi - m\phi^* \phi +\sum_{\alpha =1} ^2 ( \overline{\psi}^\alpha (i\gamma^\mu \partial_\mu -m)\psi^\alpha -g\overline{\psi}^\alpha\psi^\alpha \phi^* \phi) $$ , where ##\phi## is a complex...
  11. R

    I Are some elementary particles too massive to obey QM?

    I understand photons and elections fit into the probalistic rules of QM. Are there any other elementary particles (more massive) that don’t obey the point/wave duality?
  12. R

    I Do elementary particles experience gravity?

    For example, do electrons, atoms etc. experience gravity? Is this proved by experiment?
  13. A

    Finding initial velocity of two elementary particles

    <Moderator's note: Moved from a technical forum and thus no template.> I'm not sure how they got the extra (1/2)mv^2? My question is shown using pink font in the image below as well as my attempt.
  14. LeInvertedPenguine

    I How elementary particles form matter

    Hello, So i wonder how elementary particles which are said to have no physical extension on a larger scale are able to form what is known to us as matter? Aka stuff with an observable physical extension.
  15. Nathan Warford

    B What are the predicted sizes of elementary particles?

    I understand that the Standard Model of QFT treats elementary particles like the electron, quark, photon, muon, etc. as point-like objects. But I've also heard that a "point-like particle" is nothing more than an idealization of a particle. Elementary particles can be treated as point-like...
  16. S

    A How do we know the spins of elementary particles?

    How do we know the spin of an elementary particle? For example, a fermion has spin 1/2; a photon has spin 1; and even the ficticious graviton has spin 2. How do we know these spins? In other words, how are these spins determined?
  17. M

    I Are elementary particles subject to inertia?

    Do elementary particles have inertial mass in the same way composite objects have? If yes, does it have an impact on the motion or on the forces that act on them?
  18. Sophrosyne

    I Why are gluons considered to be elementary particles?

    Gluons are often depicted as fundamental particles in the Standard Model. But in looking at their mechanism, it seems they are not really fundamental particles in the sense that they are fundamental, indivisible, building blocks. They are mesons- a composite quark-antiquark pair, where their...
  19. smodak

    Quantum Relativity, Elementary Particles and Black Holes

    Relativity, Elementary Particles and Black Holes by Thorne & 't Hooft Any idea what this book is and why it is unavailable? Is it a popular science book? I did not know that Thorne and 't Hooft co-authored a book.
  20. petrushkagoogol

    I Compute Relativistic Velocities of Photons & Neutrinos

    Can we compute the relativistic velocities of 2 photons or 2 neutrinos ? :))
  21. L

    I Degrees of freedom of elementary particles

    The EM wave and the photon have two degrees of freedom. Their polarization directions and spin states, respectively. But they move in space, too. I mean light has the freedom to go in all directions in space. Like a macroscopic ball in 3-D space, which can go all three directions, if there are...
  22. A

    Teaching particle physics in basic education

    Hi guys! I'm doing a research about teaching elementary particles in the middle school, something that isn't the reality in my country. Despite of the research in Physics Teaching be a lot advanced, the proposals made by them are not applied in the practice of the teachers. I want to propose...
  23. I

    B Shape of elementary particles in QFT, etc?

    Hello, I hope this is not a stupid question as I am not a physicist. But I was curious about how contenders for the so-called Theory of Everything view the shape of the elementary particles. I know that the basic idea of string theory is related to the shape of elementary particles as one...
  24. D

    Materiality of elementary particles

    Do elementary particles, e.g. electron, protons, etc, have material substance in the ordinary meaning of substance? If so, what is the substance?
  25. Islam Hassan

    Elementary Particles: Wave-Like Nature vs Travelling in Wave

    When we say that elementary particles are wave-like in nature does that encompass, lead to and necessarily imply the fact that they travel in wave-like trajectories or is wave-like displacement a separate, distinct notion from their wave-like intrinsic natures? IH
  26. Brunolem33

    Elementary particles and randomness

    From the elementary particles that science has been able to identify until now, are there any that appear to be useless, at least as far as we know? Or do all the identified particles play a role in the grand scheme of the universe?
  27. N

    Electrons are not elementary particles?

    http://www.nature.com/news/not-quite-so-elementary-my-dear-electron-1.10471 Scientists have split an electron into 3 quasiparticles in the lab, why isn't this updated on the standard model?
  28. I

    Number of elementary particles in an atom

    How Number of elementary particles in an atom are counted?
  29. N

    What if elementary particles do have size

    Is it possible that they have the structure something like we used to picture them as? For example, what if we captured an electron and zoom in with a microscope that see infinitly small distances. Is it possible that if we zoomed into the electron close enough that we would see an object...
  30. A

    Filling bag with elementary particles

    Hello.This is probably totally stupid question, but anyway... Is it possible to create bag made of particles with very strong positive charge and electrons using attracting force between them? If theoretically at least in some parallel universe yes, then if we keep shooting electrons inside...
  31. Coffee_

    Intro to elementary particles, electron - nucleus collision

    1.Problem: An electron with energy ##E## which is much higher than its restmass collides with a much much heavier particle "A" of mass ##m## which is at rest. Find the maximal transfer of four-momentum. (Elastic collision)2. Conservation of four momentum3. Everything in natural units. So I go...
  32. N

    The fundamental forces and elementary particles at absolute zero

    We all know that there four fundamental forces in nature, viz. The gravitational force The electromagnetic force The strong nuclear force The weak nuclear force Now also we know that temperature of any system is the average kinetic energy possessed by the particles of the system Now...
  33. L

    The elementary particles behave both like particles and like waves

    Its was proven that one particle can be in two places at once. I found that to be confusing because matter acts in a wave like manner through the transfer of energy. My hypothesis is that the transfer of energy moves in waves effecting more than one particle at once. In light the disperse of...
  34. Islam Hassan

    Do Elementary Particles Jiggle Like Atoms?

    Do Elementary Particles "Jiggle" Like Atoms? Like the question says, if atoms jiggle about because their constituent sub-atomic particles are moving within the atom, is this movement simple orbital/linear displacement or is there also a "jiggling" to it? If there is a "jiggle" or vibration...
  35. J

    Elementary particles pre-Higgs coupling

    My question relates to the very origin of the elementary particles. I understand that the Higgs field breaks the mass symmetry of the elementary particles and that the Higgs field-based mass value for each particle is dependent upon the strength of interaction between each elementary particle...
  36. J

    Are all elementary particles point particles?

    That's my first question. 2. If that's true, why do they have different masses? 3.Since everything is made of point particles, do the fundamental forces give the actual "size" to the particles? 4.Lastly, if they are all points, is this why matter can be compressed all the way into a...
  37. D

    Particle-Wave Duality of Elementary Particles

    Hi, I am new to this forum, and to physics in general. I have been reading the basics of General Relativity and Quantum Mechanics but am yet to learn the mathematical side. I am just trying to wrap my head around particle-wave duality and specifically, the wave quantifying of elementary...
  38. C

    Can Elementary Particles be related with irreducible representation?

    Hi, I am quite naive in Particle Physics, and I have a question that Can Elementary Particles be related with irreducible representation? Could we say scalar, vector, and spinor are irreducible representation of SO(3)? Thanks a lot! I also wish I could have some reference on...
  39. Greg Bernhardt

    Particle Introduction to Elementary Particles by David Griffiths

    Author: David Griffiths Title: Introduction to Elementary Particles Amazon Link: https://www.amazon.com/dp/3527406018/?tag=pfamazon01-20 Prerequisities: Contents:
  40. T

    What is Spin in Elementary Particles?

    Looking at the Standard model, I noticed that all the quarks and leptons have a spin of 1/2 and all of the gauge bosons have a spin of 1. Can someone give me a general definition of what "spin" is and the difference between a particle that has a spin of 1/2 and a particle that has a spin of 1?
  41. D

    Can elementary particles be created out of nothing ?

    can elementary particles be created out of nothing ? i mean in the universe ? can elementary particles just pop into existence out of nothing ? if yes, how ? BTW, i know there's no "nothing" or "nothingness".
  42. P

    Is Elementary Particles important for research in Solid State?

    Hi, So here is the contents of this Elementary Particles course: introduction to families of particles , relativistic kinematics applied to reaction cross-sections and decay rates; symmetries and conservation laws, isospin, strangeness, charm, beauty; parity and CP violation in weak...
  43. umair20

    Elementary Particles: Mass, Force & Matter

    what are mass-carrying particles,force-carrying particles and matter particles?what are their differences?
  44. M

    Electric Quadrupoles, Micro Black Holes & String Theory

    I had an exchange with Lubos Motl about this topic, in the comments here. Very briefly, there is a 2004 paper in which the author (Kjell Rosquist) considers the old idea that the electron is actually a spinning, charged (i.e. Kerr-Newman) micro black hole. Using a purely classical model for...
  45. F

    How can elementary particles spontaneously decay?

    I understand that the Tau lepton is considered to be an elementary particle. Yet, it can decay into muons and nutrinoes, etc. I can understand composit particles decaying into constituent particles. But I thought that what makes a particle elementary is the fact that it does not decay. So I'm...
  46. H

    Are The Elementary Particles Truly 'Elementary'?

    I would like to know what your, and the general physics community think about whether the elementary particles we recognise today such as fermions, bosons and leptons are truly indivisible or are just made out of something smaller. People named the atom 'the atom' because it mean indivisible...
  47. T

    The dimensions of elementary particles in quantum physics and string theory

    I noticed that in quantum physics, an elementary particle has no dimensions, and is point like, but in string theory has one dimension. Why is this?
  48. Crazymechanic

    Elementary particles, resonance

    Hello, as we know from acoustics every material or fluid has it's resonant frequency (depends on density, size and other factors) at which the material "vibrates" much more than at other frequencies. Does the same thing happen when we get higher up the frequency scale, like in Mhz or Ghz and by...
  49. TrickyDicky

    Strings and elementary particles

    I was reading the brief wikipedia entry on string and there it says that strings are one-dimensional "unlike an elementary particle which is zero-dimensional, or point-like. Quarks and electrons are thought to be made of strings." The part about zero-dimensional entities being made of...